From D&D Wiki

The Dragonslayer forms a number of arrows, total amount equal to class level, out of pure light and sends them flying at his targets. This spell can strike multiple targets with these arrow doing 1d10+Int Light Damage per arrow. They can fire these arrows in any amount, but cannot exceed the total in a single day.

At Tier 2, the arrows cause ignition on contact and the target must roll a Fortitude of 20+Intelligence or else be set ablaze, dealing 1d6 Fire damage per round for 1d4 rounds.

At Tier 3, the arrows deal an additional 1d8 Force damage, a Reflex of 15+Dexterity must be made or else the target is knocked over and dazed for 1d4 rounds. If ignited the target must now roll 25+Fortitude or else suffer Fire damage for 1d6+1 rounds.